C85 Oil Leak

A small oil leak has shown up topside and immediately behind the nosebowl
on my Zodiac 601 HD powered with a C85. As near as can be seen, the
crankcase nipple connection and hose leading to the air/oil separator is not
"wet" or showing leakage. Neither the hose nor air/oil separator are
blocked.

There is extensive riveted baffling around the crank/prop flange area which
blocks a direct visual inspection.

Having heard about leaking crank front oil seals, is the replacement method
a total engine case split or some kind of split ring seal similar to old
chevy small blocks?

any help would be appreciated, thanks, Dick